Microstructure and texture evolution during equal channel angular extrusion of interstitial-free steel : effects of the die angle and processing route
Die angle (Phi) and processing route are two important factors that greatly impact microstructure and texture developments during equal channel angular extrusion (ECAE). In this study, the microstructure and texture evolution in interstitial-free steel during ECAE using a Phi=120 die are investigated for up to four passes via three routes (A, BC and C). Finite element simulations and polycrystal modeling using the Taylor and viscoplastic self-consistent models are conducted to help understand deformation behavior and texture formation. Transmission electron microscopy results reveal remarkable microstructural differences between various observation planes for each billet. The effects of Phi and processing route are discussed by comparing the current results with those for the same material processed via the same routes but using a Phi=90 die. The efficiency of grain refinement is found to be only mildly dependent on Phi and processing route. The textures can be completely characterized by predefined ideal fibers, regardless of processing route and pass number. With the exception of even-numbered passes in route C, textures developed after the same route and pass number, but different Phi can be approximately related by a rotation about the axis normal to the flow plane and the rotation angle is half of the Phi difference.